The present invention relates to an electromagnetic wave diffraction device which is intended to equip an electrically conductive wall or an electrically conductive outer wall of a building, an electrically conductive wall equipped with such a device, and a building equipped with such a diffraction device or such an equipped wall.
The invention relates to the general field of the reflection of electromagnetic waves, radio waves in particular, and more particularly to that of the prevention of the effects of the radiofrequency waves reflected by structures such as building frontages on the space surrounding such structures. The invention is applied more particularly in an airport area in order to prevent disturbances from disrupting the radiofrequency measurement systems.
Because of the presence of numerous radiofrequency sources, notably the ILS antennas themselves, the problem of stray reflections by the buildings is a significant problem, the solving of which generally involves preparing a layout plan made up of areas, notably the areas relatively close to the runways where it is prohibited to place any construction of the slightest size. Now, given, notably, the urban concentration and the desire to place airport areas at relatively short distances from the urban areas, it is becoming increasingly necessary to maximize the rate of occupancy of the airport areas in terms of surface. Consequently, finding a solution to the problems of stray reflections of radiofrequency signals in sensitive directions appears more than ever topical.
The document FR-A-2 983 577 describes a diffraction device which comprises a plurality of conductive tubular resonant elements which are arranged periodically and parallel on an outer wall of a building.
The section of each tubular element takes the form of a rectangle of which one face is fixed onto the outer wall of the building, two wings, each secured to one of the ends of the face and at right angles to the face, and two fins, each secured to one of the wings and parallel to the face and the free ends of which are separated by a slot. The capacitance is then formed by the slot.
This slot is oriented outwards and is therefore subject to bad weather. When it rains, the slot and the fins which delimit it are in contact with the water. Since water can be polarized, the capacitance of the diffraction device is increased and its effectiveness is reduced.